The National Union of Journalists has called two 48-hour strikes that could hit BBC News coverage from next week and threatened further industrial action over Christmas, after members today voted to reject management's revised pension proposals.

Approximately 70% of the NUJ members who voted rejected what director general Mark Thompson referred to earlier this month as a "final offer" on changes to the BBC's final salary pension scheme.

The other four broadcasting unions representing BBC staff – Bectu, the Musicians' Union, Equity and Unite – all voted to accept the revised offer.

Members of the NUJ, the second-largest BBC union with around 4,000 members, will strike for 48 hours on 5 and 6 November, and then again on 15 and 16 November, with "further dates to be named in the coming days". NUJ members are also introducing a work-to-rule regime from 5 November.

The NUJ has already raised the possibility of a walkout over the Christmas period.

"This massive vote against the BBC's latest proposal comes as no surprise, given the fundamental 'pay more, work longer, get less' nature of the offer," said NUJ general secretary Jeremy Dear. "NUJ members across the BBC have consistently dubbed the proposals a 'pensions robbery'. That hasn't changed. The BBC have now left members with no choice but to take action to defend their pensions."

It is not known how many of the NUJ's 4,000-strong membership participated in the ballot. The dates for the first strikes have been determined by the fact that the NUJ has to give management seven days' warning of industrial action.

It is understood that BBC management expects to push ahead with implementing the pension changes, which it argues are even more "realistic, affordable and fair" than when they were first tabled given the recent licence fee settlement with the government that will lead to a funding cut of 16% in real terms over four years from April 2011.

Senior BBC executives intend to "urge the NUJ to reconsider" its position over the period until 15 November, while it conducts a consultation with non-union staff, who account for roughly 60% of the corporation's 17,000 employees.

The NUJ is keen to point to a solidarity among the unions. Bectu, which is the largest union at the BBC and enjoys a particularly strong relationship with the NUJ, said today it is "confident of maintaining an excellent working relationship during the dispute with management".

NUJ officials also believe that if management were to attempt to get non-NUJ staff to cover during strike days or work to rule action it would receive short shrift "particularly among Bectu members", as "a lot of anger remains" despite the different outcome of their respective ballots.

Bectu has 5,500 BBC members and of those who voted, 65% chose to accept the BBC management proposal. Unite's vote was 82% in favour, while Equity and the Musicians' Union, which held meetings but not a ballot, also returned yes verdicts.

In an internal email to all staff after the union ballot results today, Lucy Adams, director of people at the BBC, said management was "very pleased that the offer was accepted by the majority of union members". She added that NUJ members represent 17% of all BBC staff.

"The acceptance by the majority of the unions reflects the feedback from staff at our pension seminars," said Adams. "Given this union result and feedback from non-unionised staff we will now implement the pay review offer and expect to go ahead with our final pensions offer when we conclude our consultation."

Adams re-iterated that no further improvement in the pension offer was feasible, at least not without cutting staff numbers and some services.

"Following the government's announcement last week of the BBC's new licence fee settlement we will be required to find stretching savings across the organisation in addition to our current efficiency targets," she said. "As we have previously communicated to the unions, this is our final pensions offer and we cannot afford to make any further adjustments without impacting on jobs and services."

Bectu revealed that when its figures were broken down to show how members at BBC Worldwide voted, the ballot was a resounding 89% in favour. Bectu members in the main licence fee-funded BBC balloted 65% in favour of management's proposals.

"There is no hiding the fact that even with the improvements we have negotiated members will in future have less favourable terms than exist currently," said Bectu general secretary Gerry Morrissey. "[However] I believe that the outcome of these talks, given the climate which the BBC and other public bodies face today, represents a decent settlement for BBC staff and is one that would not been have been achieved without the enduring support of our members and their local representatives."

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